In the coming year our research efforts will be concentrated on study of the optic nerve from the eye to the chiasm. Chick embryos of varying ages will be used and most of the studies will be done by electron microscopy. By making small lesions on the retina and then continuing the incubation period so that the lesioned optic axons degenerate, we will attempt to determine if: (a) axons originating from different parts of the retina vary in diameter, (b) axons originating from a small local region on the retina are grouped in one or several fascicles, and (c) the size of fascicles is related to spatial origin. Other studies using older embryos and newborn chicks will be done to determine the interaction that occurs at the chiasm between fibers from each eye, including their orientation to each other and any evident forces that may guide fibers to the contralateral side. These studies on the optic chiasm will be done in both control animals and animals that had unilateral eye enucleation.